Year	Percent
1970	83.15789
1971	83.74194
1972	84.3038
1973	84.84472
1974	85.36585
1975	85.88517
1976	86.48649
1977	87.06697
1978	87.64172
1979	88.18283
1980	88.71851
1981	89.23574
1982	89.83051
1983	90.3125
1984	90.87179
1985	91.42281
1986	91.94831
1987	92.45837
1988	92.95367
1989	93.43482
1990	93.90244
1991	94.35708
1992	94.88584
1993	95.22523
1994	95.64057
1995	96.04569
1996	96.44097
1997	96.74099
1998	97.1162
1999	97.40151
2000	97.76119
2001	98.03117
2002	98.37662
2003	98.63454
2004	98.88712
2005	99.05586
2006	99.29907
2007	99.53704
2008	99.77064
2009	100
2010	100.15004
2011	100.37202
2012	100.51622
2013	100.65789
2014	100.8702
2015	100.93458